Not Applicable
This invention relates to materials transport systems and more particularly to a system for moving semiconductor wafers or other materials to various locations along a track and having inductive power transfer from the track to cars moveable along the track.
Computer controlled materials transport systems are known for moving materials among various work stations of a facility. Such systems are employed, as an example, in semiconductor fabrication facilities for moving semiconductor wafers to successive work stations. In such a wafer transport system, a monorail track is routed past the work stations and a plurality of cars are mounted on the track and moveable there-along for delivering wafers to successive work stations and for removing wafers therefrom after requisite processing operations have been accomplished. The track is composed of interconnected track sections which usually include one or more routing sections or modules which are operative to provide plural paths along the track. The car includes one or more motors coupled to drive wheels which in turn engage the track for propelling the car along the track. Electronic circuitry governed by an on board micro-controller controls operation of the car in response to control signals provided from a central control point or multiple control points within the facility. A battery or battery pack is contained on board the car for powering the motors and associated circuitry. A materials transport system used for semiconductor wafer transport and other materials is described in U.S. Pat. No. 4,926,753 which is assigned to the same Assignee as the present invention.
The battery on board the moveable cars must be periodically charged to maintain their effectiveness. Heretofore such charging has been accomplished at predetermined positions along a track at which a car is stopped and at which position the battery of the car is coupled to a charging source by electrical contacts which are engaged when the car is at the stationary charging position. The electrical contacts can become worn or contaminated over time, and as a result performance is degraded. The contacts are also a source of electrical interference which can affect surrounding electronic equipment.
In accordance with this invention an inductive power transfer apparatus is provided which is especially useful for a semiconductor wafer handling system or other similar type of materials transport system in which one or more cars are moveable along a track. This system includes a plurality of elongated primary transformer coils each disposed at an intended position along the track. Each of the moveable cars has one or more pick-up or secondary coils which are coupled to the primary coil when the car comes into position along the track. The secondary coil or coils on the car provides power to a battery charging circuit for so long as the secondary is in coupling relationship with the primary or for so long as needed to provide an intended charge to the on board batteries or other energy source. A drive circuit for the primary coil may be located near the primary coil or alternatively, a single drive circuit can be at a central location to provide drive signals to a plurality of primary coils.
Preferably the drive circuit is inactive when the secondary coil is not in coupling relationship with the primary coil and the drive circuit is rendered active when the secondary is in coupled relationship with the primary coil. The drive circuit is powered from a DC source and provides a pulse or other non-DC wave shape to drive the primary coil. In one embodiment the primary coil is controlled by a signal from the secondary or from a separate detector to provide feedback control of the charging cycle. A detector can be provided in association with the primary coil to detect the presence of the secondary coil to thereby energize the primary coil for power transfer. Intelligent control can be provided such that the secondary can determine how much charge is needed for the associated battery, and control signals applied to the primary circuit to govern the pulse rate of the primary power drive and thereby determine the amount and duration of power that is provided by the primary coil to the secondary coil and thence to the battery.